Various scientific instruments comprise pressurized chambers, either containing regions of low or high pressure, or containing a vacuum. In order to adjust or move one or more components in the chamber, an actuator can be used to apply a force to move the component. Known adjustment mechanisms make use of actuators comprising, for example, threaded rods, or thermoelectric or piezoelectric elements. These types of adjustment mechanisms have the disadvantage that at least a portion of the actuator or a connection to the actuator must be provided at sealed feedthroughs in the wall of the chamber. This both increases complexity and increases the likelihood of leakage of the pressurized chamber.
Spectrometers, especially mass spectrometers, require an ion beam path to pass through a slit or aperture within a vacuum chamber. It is useful to be able to select the width or dimensions of the slit or aperture, depending on the requirements for maximum sensitivity or maximum resolution of the measurement. In order to provide a variety of aperture dimensions for use in the mass spectrometer, an aperture plate is included which comprises multiple apertures of different dimensions. The aperture plate can be moved within the vacuum chamber for alignment of the chosen aperture with the ion beam. As it is not desirable or practical to open the vacuum chamber to move the aperture plate, an adjustment mechanism is required which can be operated from outside the chamber.
U.S. Pat. No. 5,451,780 describes a device for setting slit widths in the beam path of spectrometers. The device uses a lever which is pivotally connected within the vacuum chamber, and which has slits of different dimensions at one end of the lever. A Bourdon tube is connected to the opposite end of the lever furthest from the slits. When the pressure in the Bourdon tube is increased, the lever is rotated around the pivot to cause a different aperture to be bought into alignment with the ion beam. The connection to the Bourdon tube is required through the wall of the vacuum chamber.
The known adjustment mechanisms each require connection to an actuator through the walls of the chamber. As such, these connections must be correctly sealed and maintained in order to prevent leaks to the chamber.
In view of the above, there is a need to provide an improved adjustment mechanism for effecting adjustment of a moveable element inside a sealed or closed chamber.